1. Field of the Invention
The disclosed embodiments of the present invention relate to a low-dropout voltage regulator mechanism, and more particularly, to a low-dropout voltage regulator apparatus which is capable of adaptively adjusting the current passing through the output transistor to reduce the transient response time and related method thereof.
2. Description of the Prior Art
Generally speaking, a conventional low-dropout (LDO) voltage regulator generates and outputs a stable output voltage to the following circuit under an ideal operation. However, in practical designs and operations, loop bandwidth of a low-dropout voltage regulator may have a frequency range from hundreds of KHz to dozens of MHz. Therefore, the conventional low-dropout voltage regulator has a poor transient response for an output current load. For instance, when the load of the conventional low-dropout voltage regulator is changed from a light load to a heavy load, the conventional low-dropout voltage regulator requires more transient response time to provide a stable and balanced output current for the following circuit. Hence, the load change of the conventional low-dropout voltage regulator induces a dramatic voltage change such as a voltage dip. In addition, when the load of the conventional low-dropout voltage regulator is changed from a heavy load to a light load, the conventional low-dropout voltage regulator requires more transient response time to gradually reduce the degree of conduction of the output power transistor. Hence, the load change of the conventional low-dropout voltage regulator induces a dramatic voltage change such as a sudden voltage jump.
A conventional solution is provided with a very large external regulating capacitor intended to reduce the dramatic voltage change at the transient response time; however, this very large external regulating capacitor not only dramatically increases the production cost, but also reduces the original loop bandwidth and thus deteriorates the regulator performance.